Nano fibers are a fiber material having the diameter less than hundreds of nanometers.
Fibers may be divided into single-component, two-component and multi-component fibers according to cross-section structures. The single-component fibers are fibers constituted on the cross-sections thereof by one material or a uniform mixture of several materials. The two-component fibers are fibers having a certain special regional structure relation on the cross-sections thereof constructed by two materials with different components. The two-component fibers and the multi-component fibers fall into the scope of composite fibers, wherein each component may be a single material or a mixture of several materials. By a structure relation between the two components, the two-component fibers may be divided into fibers of a bilateral (also referred to as conjugated) structure, fibers of a core-shell (also referred to as shell-core or core-sheath or concentric or coaxial) structure, fibers of a sea-islands structure, tip-covered fibers, segmented fibers and the like.
The nano fibers are extremely high in specific surface area and transverse-longitudinal ratio. For example, fabrics woven using the nano fibers are fine in structure, extremely high in porosity, and excellent in flexibility, absorptivity, filterability, adhesivity, heat retaining property and mechanical strength. These unique characteristics allow novel properties of the nano fibers that micron fibers lack, and the nano fibers thus have been extensively applied in a variety of fields. In recent years, scientists have found that by combining the two-component or multi-component composite micron and nano fibers having special cross-section structures, i.e., two materials having different properties, micron and nano fibers having completely new properties that many single-component fibers lack or better properties than those of the single-component fibers. The two-component or multi-component composite micron and nano fibers have more favorable application prospect in many important high-end fields, for example, such fields as protective clothing, biomedical articles (tissue scaffold structures, artificial human body organs, wound dressings, medicine release, etc.), membrane materials, filter media, catalysts, electronic products, energy storage and composite reinforcing materials.
At present, a traditional textile device is able to produce the two-component micron fibers, but fails to realize large-batch and low-cost production of the single-component, two-component and multi-component micron and nano fibers with various structures on one machine. At present, a spinning device for producing the single-component, two-component and multi-component micron and nano fibers with various structures mainly employs a needle electrostatic spinning method. Briefly, in the needle electrostatic spinning technique, a high-voltage power source produces a high-voltage electrostatic field between needles of syringes filled with spinning solutions and an electrically conductive collecting apparatus such that the spinning solutions in the syringes are sprayed from the needles by overcoming surface tension under the action of the high-voltage electrostatic field to form nano fibers on the collecting apparatus. Nevertheless, the needle electrostatic spinning method is extremely low in yield, requires high voltages resulting in high work safety risk and high cost, and additionally may be greatly influenced by such properties as the concentration and viscosity of the solution and cannot be easily produced at a large scale.